An interventional study of Intervention A - Electromyography (EMG)-Guided BTX Injection and Intervention B - Endoscopic Catheter BTX Injection in Spasmodic Dysphonia, sponsored by Chinese University of Hong Kong. Not yet recruiting. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-26.
Sponsored by Chinese University of Hong Kong · Not applicable, Interventional, and Treatment
This randomized, controlled non-inferiority trial will compare two established botulinum toxin injection techniques for adductor spasmodic dysphonia: percutaneous electromyography-guided injection and transnasal endoscopic catheter-guided injection. The study will evaluate whether the endoscopic technique provides voice outcomes that are not inferior to the standard EMG-guided approach, while also assessing treatment-related adverse effects, procedural tolerability, and practical advantages such as direct visualization and suitability for patients with challenging neck anatomy.
Spasmodic dysphonia (SD) is a rare neurological disorder caused by involuntary and intermittent spasms of intrinsic laryngeal muscles. Depending on the intrinsic muscles involved, SD is typically classified into 3 types: Adductor SD (AdSD), abductor SD (AbSD), and mixed SD. AdSD is the most common form of SD, and is a task-specific laryngeal dystonia involving the thyroarytenoid (TA) and lateral cricoarytenoid (LCA) muscles during phonation, resulting in a strained, strangled, and effortful voice with intermittent voice breaks. Symptoms typically first manifest in the mid-30s and may persist as a lifelong condition.
While there is no cure for AdSD and high rate of long term failure with surgical treatment, botulinum toxin (BTX) injection into the TA muscles has been established as the gold-standard treatment for AdSD since the 1980s, with a success rate in voice symptoms improvement up to 90%. BTX blocks acetylcholine release at the neuromuscular junction, producing reversible chemodenervation of the hyperactive intrinsic laryngeal musculature. Relief typically commences within a few days post-injection, with voice improvement lasting approximately 3-4 months before symptom recurrence, requiring repeated injections.
Several techniques have been developed over the years for the administration of BTX into the adductor compartment. The well-established percutaneous electromyography (EMG)-guided approach targets the TA/LCA complex in a transcricothyroid manner, where a needle is introduced through the cricothyroid membrane under real-time EMG feedback and allows confirmation of correct muscle placement during phonation. With the advancements of surgical endoscopes, the endoscopic-catheter injection approach has been a recently described technique also favoured by many surgeons. It is performed transnasally using flexible laryngoscopes, allowing for direct visual confirmation of needle placement into the TA/LCA muscle and false cord via a working-channel catheter.
Proposed benefits of the transnasal endoscopic-catheter approach include the ability to divide BTX injections into sub-doses targeting TA/LCA muscles and false cords, instead of injecting as a whole block as in the EMG-guided approach, potentially producing less breathiness as less total dosage is administered on any one TA muscle. Additionally, it might be particularly useful in cases with anatomical limitations, such as those with non-palpable neck landmarks or poor neck exposure with difficulty/inability in neck extension.
Despite the widespread use of both methods, no randomized controlled trial has directly compared their functional outcomes in a rigorous non-inferiority framework. Previous prospective trials have compared the EMG-guided approach to other methods such as the "point-touch" approach or the endoscopic-guided percutaneous injection approach , showing similar effectiveness amongst these techniques. However, no previous studies have compared the EMG-guided approach to the transnasal endoscopic-catheter approach. It is therefore important to establish non-inferiority of the transnasal endoscopic-catheter approach and capture the comparative advantages and limitations of the two techniques under a randomised and controlled trial setting.
132 studies on the registry are indexed under Dysphonia; 38 are open to participants now.
This study's planned enrollment of 17 is below the median of 30 across 87 interventional studies indexed under Dysphonia.
Browse Dysphonia studies →Chinese University of Hong Kong is the lead sponsor of 1,454 studies on the registry; 474 are open to participants now.
Of its 6 completed or terminated interventional studies of FDA-regulated products, 0 (0%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Arm EMG: Each participant will receive Intervention A (EMG-guided injection) at Week 0; then a washout period of 14 weeks; and finally followed by Intervention B (endoscopic catheter injection) Crossover injection (opposite intervention) at Week 14.
Procedure: Intervention A - Electromyography (EMG)-Guided BTX Injection · Procedure: Intervention B - Endoscopic Catheter BTX Injection
Arm endoscopic catheter : Each participant will receive Intervention B (endoscopic catheter injection) at Week 0; then a washout period of 14 weeks; and finally followed by Intervention A (EMG-guided injection) Crossover injection (opposite intervention) at Week 14.
Procedure: Intervention A - Electromyography (EMG)-Guided BTX Injection · Procedure: Intervention B - Endoscopic Catheter BTX Injection
The patient is positioned comfortably with the neck slightly extended. Surface reference and ground electrodes are applied. After application of EMLA cream (lidocaine 2.5%/prilocaine 2.5%) and disinfection of the skin, a 27-gauge needle electrode connected to an EMG machine is introduced percutaneously through the midline of the cricothyroid membrane and angled superiorly and laterally toward the TA muscle. Correct placement is confirmed by characteristic bursts of motor unit activity on phonation. Once confirmed, BTX is injected. The whole procedure including post-operative observation takes approximately 90 minutes. Vital signs and oxygen saturations are monitored throughout the procedure.
Following administration of topical anesthesia with 5% lidocaine/0.5% phenylephrine (Co-phenylcaine) nasal spray and topical Xylocaine laryngeal spray via working channel, a transnasal channel flexible bronchoscope is introduced. A sterile catheter needle is introduced via the working channel of the bronchoscope, and BTX is injected directly into the TA/LCA muscle and false cord under direct visualization. The whole procedure including post-operative observation takes approximately 90 minutes. Vital signs and oxygen saturations are monitored throughout the procedure.
Change from Baseline in Voice Handicap Index (VHI-30) at 4 weeks post-operation
The Voice Handicap Index (VHI-30) is a 30-item self-administered patient-reported outcome measure for voice-related disability, comprising physical, functional, and emotional subscales. In a scale of 0 (Never), 1 (Seldom), 2 (Occasionally), 3 (Frequently) and 4 (Always). Score range 0-120; higher scores indicate greater handicap. Baseline total score of Voice Handicap Index (VHI-30) will be subtracted from 4-week post-operative total score.
Time frame: Baseline and 4 weeks post-operation
Change from Baseline in Perceptual Voice Quality Total Score on the Grade, Roughness, Breathiness, Asthenia, Strain (GRBAS) Scale at 12 weeks post-operation
Perceptual rating of voice quality will be evaluated using the GRBAS scale. The scale consists of 5 components: Grade (G), Roughness (R), Breathiness (B), Asthenia (A), and Strain (S). Each component is scored from 0 (normal) to 3 (severe). The total score is calculated by summing the scores of all 5 components. Total scores range from 0 to 15, where a score of 0 represents normal voice quality and a score of 15 represents the most severe voice impairment. Higher scores indicate a worse clinical outcome. Baseline GRBAS total score will be subtracted from the 12-week post-operative total score. A negative change score indicates an improvement in voice quality, while a positive change score indicates a worsening of voice quality.
Time frame: Baseline and 12 weeks post-operation
Change from Baseline in Perceptual Voice Quality Total Score on the Grade, Roughness, Breathiness, Asthenia, Strain (GRBAS) Scale at 4 weeks post-operation
Perceptual rating of voice quality will be evaluated using the GRBAS scale. The scale consists of 5 components: Grade (G), Roughness (R), Breathiness (B), Asthenia (A), and Strain (S). Each component is scored from 0 (normal) to 3 (severe). The total score is calculated by summing the scores of all 5 components. Total scores range from 0 to 15, where a score of 0 represents normal voice quality and a score of 15 represents the most severe voice impairment. Higher scores indicate a worse clinical outcome. Baseline GRBAS total score will be subtracted from the 4-week post-operative total score. A negative change score indicates an improvement in voice quality, while a positive change score indicates a worsening of voice quality.
Time frame: Baseline and 4 weeks post-operation
Glottal Closure Type at 4 weeks post-operation
Glottal closure configuration will be assessed by videostroboscopy according to the pattern of vocal fold contact during phonation and classified as: 1 = Complete closure; 2 = Anterior Gap; 3=Posterior Gap; 4=Hourglass gap; 5 = Spindle gap; 6 = Irregular gap; 7 = Incomplete closure. A lower numerical category, particularly a transition from an open-gap configuration (categories 2-7) to complete closure (category 1), will be considered an improvement in vocal fold function.
Time frame: 4 weeks post-operation
Glottal Closure Type at 12 weeks post-operation
Glottal closure configuration will be assessed by videostroboscopy according to the pattern of vocal fold contact during phonation and classified as: 1 = Complete closure; 2 = Anterior Gap; 3=Posterior Gap; 4=Hourglass gap; 5 = Spindle gap; 6 = Irregular gap; 7 = Incomplete closure. A lower numerical category, particularly a transition from an open-gap configuration (categories 2-7) to complete closure (category 1), will be considered an improvement in vocal fold function.
Time frame: 12 weeks post-operation
Peri-procedural pain at Day 1
The Numeric Rating Scale (NRS 0-10) is a 11-point self-report tool used to measure peri-procedural pain intensity, where 0 represents "no pain" and 10 represents "the worst pain imaginable".
Time frame: Day 1
Procedural tolerability at Day 1
Procedural tolerability using a Numeric Rating Scale (NRS) 0-10 measures how well a patient can accept and withstand the study intervention, where 0 means no pain or discomfort, the fully tolerable and 10 means the worst imaginable pain or most intolerable experience possible.
Time frame: Day 1
Difficulty of performing the intervention at Day 1
The Numeric Rating Scale (NRS) is an 11-point scale (0-10) that can be adapted by a surgeon to quantify the technical difficulty or complexity of performing the study intervention. In a scale of 0 (very easy) to 10 (very difficult).
Time frame: Day 1
Change from Baseline in Voice Handicap Index (VHI-30) at 12 weeks post-operation
The Voice Handicap Index (VHI-30) is a 30-item self-administered patient-reported outcome measure for voice-related disability, comprising physical, functional, and emotional subscales. In a scale of 0 (Never), 1 (Seldom), 2 (Occasionally), 3 (Frequently) and 4 (Always). Score range 0-120; higher scores indicate greater handicap. Baseline total score of Voice Handicap Index (VHI-30) will be subtracted from 12-week post-operative total score.
Time frame: Baseline and 12 weeks post-operation
No study locations are listed for this record.
Plan to share: Yes
Supporting information: Study protocol
No publications or documents are linked to this record.
Start is estimated for Oct 2026; primary completion for Apr 2029, 30 months later.
Of 44 non-industry interventional studies with no phase under Dysphonia, half reached primary completion within 26 months of starting (the median), counting those still running; a quarter within 11 and three quarters within 47. This study's planned 30 months is above that.
Counting every sponsor, half of 44 studies reached it within 26 months; a quarter within 11 and three quarters within 47.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Chinese University of Hong Kong →